1. Field of the Invention
The present disclosure relates to an oxynitride-based phosphor having a novel crystal structure and a light emitting device including the same.
2. Description of the Related Art
In general, a white light emitting diode (LED) recently prominent due to the use in lighting devices, LCD backlights, automobile lighting devices, and the like, includes an LED emitting blue or near ultraviolet light and as an excitation source, a phosphor converting a wavelength of the light emitted from the LED into visible light.
A representative method of implementing the white LED includes employing a blue LED formed of an InGaN-based material having a wavelength of 450 to 550 nm as a light emitting element and employing a YAG-based phosphor emitting yellow light and represented by a compositional formula of (Y, Gd)3(Al, Ga)5O12 as a phosphor. In the white LED, blue light emitted from the light emitting element is incident on a phosphor layer and repeatedly absorbed and scattered within the phosphor layer. Yellow light formed by wavelength converted blue light and a portion of the incident blue light are mixed, such that the blue light absorbed in the phosphor through the repeated process may appear to human eyes as white light.
However, the white LED having such a structure has few red light components in light thereof, a high color temperature, and insufficient green light components, and thus, merely functions as illumination light having low color rendering properties.
In addition, oxide-based phosphors generally tend to be degraded in terms of luminous intensity when a wavelength of an excitation source is above 400 nm, and accordingly, are not appropriate for implementing white light having high brightness using blue light.
Therefore, oxynitride-based phosphors having excellent luminous efficiency in the case in which a wavelength of an excitation source is above 400 nm, while having stability equal to or greater than that of oxide-based phosphors, have recently been receiving attention in white LED application fields. The oxynitride-based phosphors are materials originally developed as engineering ceramics and thus, have a low reduction in efficiency and low levels of color change due to moisture or heat.
However, research into oxynitride-based phosphors present in a compositional area outside of α-type or β-type sialon (Si—Al—O—N) phosphors, has not been greatly undertaken or is little known.